Stratospheric reproducing cabinet



Filed Oct. lO, 1944 Patented July 26, 1949 UNITED .STATES PA'lfllNflV l CEl ASTRATOSPHERIC REPRODUCINGCABINET Ronald .Vin'goe, Wellington, -Ohio Application October 10, 1944', Serial No. 558,061

3 Claims.

(Granted under the act of .March 3 1883, ,as amended April 30, 1928; 370. O. G. 757) The invention'described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to laboratory equipment and more particularlyto means for maintaining stratospheric conditions- Within an enclosed chamber that is adapted for being installed in laboratories and the .like at ground levels.

With the advent of highaltitude flying during the present War, new impetus has been imparted of necessity to the investigation of the limitations of airborne equipment that are expected to function satisfactorily when subjected to the physical conditions that are encountered there. Heretofore the study of the matter has been limited very largely to the observation and the recording of the effects upon equipment and personnel of the physical conditions encountered at high altitudes. Actual flights to extremely high altitudes for the purposes of testing, improving and perfecting the equipment to be used are in some instances necessary, but in the majority of cases have been unsatisfactory, time-'consuming and wasteful of effort Without commensurate returns.

For some time past it has been possible and desirable to send highly sensitive and delicate `instruments into the stratosphere as Well as to lesser high altitudes Where the instruments are to function under .physical conditions that differ widelyV from the Vlaboratory conditions under which the instruments are designed to deliver their optimum performance. The principal differences in physical conditions under which it is desirable that instruments and the like be adaptf ed tocontinue to deliver optimum performances are in temperature, pressure, humidity, absence of particles, and partial ionization of the air, A study of the properties of air at altitudes up to 70,000 feet indicates that further control is desirable, particularly over dewpoint, freedom from contamination, and increased ionization of the gases present, yThe .variations in the performances of instruments at high altitude conditions appears to be particularly apparent in radio equipment kand in equipmentY having moving or rotating parts.

. .The objects of the present invention include the provision ofmeans for maintaining stratospheric conditions in a suitable enclosed laboratory cabinetfor chamber -wherein yradio sets, equipment and the like, may be removably disposed and operated under physical .conditions that substantially duplicate conditions at altitudes upto. 70,000 feet. ,iy

With the above andotherobl'ectsinvi-ew which will be apparent to; those whoare informedin the field k of-,development in which,i the :present invention belongs, lan:;illustrative .diagramzand ow sheet of a preferred foiambff` deviceisfshown in the accompanying drawing wherein:

Fig. 1 is a flow sheet;.;indicatingthe:chosen or preferred `manner of :'.conditioningland v.maintaining air in a predetermined physical state Within a suitable closedcabinet orchamber1 The cabinet that is.;to be usedin conjunction with the herein-described method-'of processing air that is to provide a ydesired atmosphere Within the cabinet, has, an interior thatris sealed from contact with the ambientair. .The'cabinet I is lined preferably with a material -thatmay-bekept at a maximum degreeof. cleanliness and freedom from contaminates, suchas; stainless steel or the like. The cabinet l. preferably. is well insulated and is maintained vat apredetermined low ternperature, as ybyhaving.,cooling coils or the like preferably built into its walls.

o All pumps, fan motorsand the like, that are used in. conjunction withlthe cabinet, are preferably mounted outside of lthe, cabinet .and are sealed against causingv any44 contamination of the conditioned air Within thericabinet-by oil vapors, dustfparticlesor the ylike,.from.the pumps and motors used with the system.

When the chamber-or cabinet kI iszmechanically clean, the radio ora'other apparatus-to be tested is positioned. therein and Athe leads.v thereto are connected with ttings Within the cabinet that extend through the walls'of the-cabinet l so that the apparatus ycanbeoperated and adjusted from cutside of the :cabinet l.

The system is first iushedioutfwithair by admitting rand filtering-:compressed air from the compressed air line Zand released through a discharge valve 3 `for afdesired period of time until all.V ofv the moisturefand-contaminants that can be eliminated from the` system by this means have been removed. A 4valve lA -rin theycompressed air line 2 and the dischargezvalve 3 are `then closed. A vacuum line valve 15. is athen.'openedl and the system evacuated :after which an ambient air line valve B isopenedfandv lambient i'air is drawn lthrougnthe system. The ambient air may be drawnfzthrough a suitable rfilterA (not shown) beiore entering-the ambientair'lin'e 1. The purpose of this filtering step is to remove any foreign matterpresentfin'thefambient air-that might foul the pr'edryers r`I I. If .the :ambientair-issufficiently free of foreigncmatteri-th filtering s tep may be omitted. The :ambient i airfthen --passes through the ambient air line 1 and the connecting line 8 to branched feeder lines 9, each provided with a gat- Y ing valve I to individually serve either or both of a pair of refrigerating predryer tanks I I.

The refrigerating predryer tanks I I remove excess moisture from the filtered ambient air sufficiently to4 prolong theflife period of additional drying tanks 'furtheralong in the system which serve to remove the traces of moisture that pass through the predryer tanks II. The predryer tanks II are of the refrigeration type and precool the ambient air together with the condensation of Water therefrom. In the predryertanks.

ak feeder line 32 that conducts it to a filter'33.

Y A bypass 34, closed by 'a valve 35, joins the `connecting line I8 with the feeder line 32 for use where it is desirable that the processing of the vcirculated air by the calcium sulfate towers 2I,

indicator 24 and precoolers 28 is not necessary.

l j A bypass`36, closed by a valve 31, connects the II the filtered ambient airis chilled until Vall moisture in excess of saturation at the temperature there maintained is condensed out and ref-.

moved from the ltered ambient air that Vpasses connecting line 25 with the feeder line 32, for use Where the effect of the precoolers 28 upon the circulated air is not necessary. A bleeder 3B opening to theV ambient atmosphere and closed by a 4 Yvalve 39 is provided in the feeder line 32 to bleed beyond the refrigerating predryer tanks I I. Suitf able means, such as water bleeders I2 that arev closed to the outside airvby valves I3 or the like, serve to remove the condensed Water that accumulates Within the Vpredryer tanks II. l The predryer tanks II may be refrigerated any desired manner, asby the use of coils, tanks, or the like, through which a desired refrigerant is caused to flow. A suitable air refrigerant means that has been found to perform satisfactorily in Van vexperimental installation Vcomprised a mixture of Dry Ice and acetone with which the conducted air was in direct contact. In this installation, the filtered ambient air entered the refrigerating predryers I`I through an aperture n the outer wall and the moisture in the ltered ambient air condensed and solidified Yupon th inner Walls of the predryers II.

Suitable discharge lines I4, that are separately gated by valves I5, converge into a filter feed line I6 that opens into an activated carbon lter I1. The activated carbon filter I1 effectually removes traces of oil vapors, organic vapors, odors andother contaminants from the ltered and refrigerated ambient air that passes through it.

The filtered and refrigerated ambient air that into a connecting line' I8 from which it enters into either or both feed lines I9, that are individually gated by valves 20, and thatconduct the air to calcium sulfate towers 2I where the last traces of water vapor are removed. The calcium sulfate towers 2| are preferably charged with the specially treated forml of calcium sulfate that iis marketed under the trade name Drierite Activated alumina will produce equallyl desirable results if used in conjunction with compressed air.

The filtered and refrigerated ambient air that passes from the calcium sulfate towers 2l is sep-` arately gated through valves 22 to a feed line 23 that conducts it to a dewpoint humidity indicator 24. The dewpoint humidity indicator 24'is preferably of the continually visible type reading directly in dewpoint values in centigrade or Fahrenheit, and serves to indicate promptly the exhaustion of the Water absorbent material in the drying towers ZI. The indicator 24 preferably consists of a transparent tube packed with a suitably treated desiccant which will change color upon the absorption of moisture such as the calcium sulfate used experimentally and treatedto change in color from blue violet to -red upon the entrance of conducted air having an undesirablyhigh water vapor content. K g

A connecting Yline 25 conducts the circulated air Yto'branclled, feeder lines 26 that are individually gated by valves 21 to precoolers 28, so that the circulated air maybe conducted to eitheror in under vacuum enough untreated atmospheric air to increase lthe moisture content of the circulated air to a desired value depending upon the reading of thedewpoint indicator 24.

The predryers I I, dryers 2 I, and the precoolers 28 are preferably installed in parallel pairsV in order that longer tests may be conducted without closing down the conditioning system to recharge theseY elements or to blow any condensed'moisture out of the precoolers vand the predryers.

A conducting line'40 connects the filter 3 with a ow meter 4I. The flow meter 4I is connested by a conducting'line 42 Withfthe altitude chamber I.v lSuitable means, such as a bypass 43 around the flow meter 4I and equipped with a valve e4 is provided for'cutting the ow meter out of the line.

The conditioned air Within the altitude cham-V ber I is ionized in any preferred vmannenand preferably by the use of an ultraviolet source 45 Within the altitude chamber I. The ultraviolet source may be in the form'of an incandescent Wire, a flame, a radioactive material, a carbon arc, or the like. The degree of ionization of the air Vwithin the cabinet I should duplicate, as nearly as is practicably possible, that of the atmosphere at the altitude at which the equipment within the chamber Vis to be tested. A safety filter 46 preferably is also provided to minimize damage to the vacuum pump from carbon dust kor other particles carried by the circulated air. A' ow meter, such as a venturi, orifcemeter, Pitot tube, or the like, may be disposed in the system, if dei sired, and preferably in therconducting line 42 that serves the altitude chamber I. An outlet line 41 connects the altitude chamber I with the filter ll. The chamber I may be of cabinet or of room size, as required for the test to be made therein.

ambient air entering the predryer II normallyV has a dewpoint within a range of from 15", C. to -l-10 C'. depending upon atmospheric conditions. The conducted air leaving the predryer I I charged with solid carbon dioxide and acetone has a (dewpoint within-grange between c; to"65 cV The conductedV air Aleaving Athe calcium sulfate Vtowers 2| has a dewpoint of '-18 C. or below,

based on atmospheric conditions. When `the system isevacuated, the Vdewpoint is further low.- ered because of the Withdrawal of conducted air and the resultant expansion of the residual air remaining within the system. The bleeder valve 39 may be partly opened, if desired, to increase the moisture vapor content of the conducted air to a desired value for an accurate reproduction of a desired moisture vapor content within the altitude chamber I.

The operation of the system is continuous during the period of testing the apparatus. In those situations where the periods of test are brief, more than a single test may be made without changing the exhaustible charges, such as the contents of the refrigerating predryers, the calcium sulfate towers, the precoolers and the iilters. Where the periods of test are prolonged, one set of the parallel air conditioning units can be used at a time by the use of the gated arrangement. Additional sets of these units in parallel may be introduced into the air conducting lines for still longer periods of test. The described cycle of operations preferably are gone through for each period of test.

Illustrative problems that are encountered in high altitude flying for the solution of which the present invention is of use include brush wear in moving electrical equipment. It has been found that above 20,000 feet altitude, carboncopper brush wear is materially accelerated and in some instances with the disintegration of the brushes. Other problems encountered during the operation of radio equipment are the presence of excessive arcing and static electricity and in some cases the complete failure of function in the radio equipment used.

Whereas in some equipment the difficulties encountered in the higher altitudes may be overcome by changes in design and by substitutions of materials or composition, other more complex problems may require repeated and prolonged experimentation before their solution is arrived at. It is with this more complex type of problem that the present invention has proven to be well adapted and reasonably satisfactory.

Activated alumina has been tried experimentally as drying agent in the system that is disclosed herein. If activated alumina is used under pressure, the dewpoint will be lowered upon ex pansion due to the same amount of moisture being contained in a larger volume. Absorbent cotton has been tried out as a filtering material but has been found to be less desirable in the present installation than activated charcoal which performs the further function of removing organic vapors from the circulated air. The removal of organic vapors is of particular importance involving dynamotor brush wear, since contaminants of this type lubricate the brush commutator contact, accelerate oxidation and their absence increases the wear rate between these moving parts. It is theorized that disintegration of brushes in the stratosphere is due to lack of moisture and impurities in the air of the stratosphere. It is believed that this absence of moisture and impurities prevents oxidation of the contacting surfaces and accelerates the disintegration of the brushes, since the presence of an oxide film between the contacting surfaces of the commutator and the brushes is believed to reduce wear therebetween. Glass wool is preferred as compared with absorbent cotton or similar organic filters because of its absence of absorption and packing, freedom from lint and its chemically inert characteristics. Infra-red rays may, if desired, be used to obtain very low dewpoints in the conducted air.

It is to be understood that the disclosed embodiment of the present invention has been submitted for the purpose of illustrating and describing one preferred form thereof and that various modications and changes may be madeI therein Without departing from the invention as defined by the appended claims.

What I claim is:

1. In a system of air conditioning, the method of reproducing high altitude physical conditions in a compartment comprising the consecutive flow steps of predrying ambient air by refrigeration, filtering the predryed air to remove foreign particles, oil vapors, organic odors, and other contaminants, drying the filtered air, testing the air for the absence of moisture therein, cooling the air, filtering the air, regulating the rate of flow of air, introducing the air into a compartment, and removing the air from the compartment after again filtering the air.

2. In a system of air conditioning, the method of reproducing high altitude physical conditions in a compartment comp-rising the consecutive iiow steps of predrying ambient air by refrigeration, ltering the air to remove foreign particles, oil vapors, organic odors and other contaminants, drying the air, testing the air for the absence of moisture therein, cooling the air, filtering the air, measuring the rate of flow of the air, introducing the air into a compartment, ionizing the air, and removing the air from the compartment.

3. In a system of air conditioning, the method of reproducing high altitude physical conditions in a compartment comprising the consecutive flow steps of predrying ambient air by refrigeration, ltering the air to remove foreign particles, oil vapors, organic odors and other contaminants, drying the air, testing the air to determine the moisture content thereof, cooling the air, mixing untreated ambient air with said treated air, filtering the air, measuring the rate of flow of the air, introducing the air into a compartment, ionizing the air While in the compartment, and removing the air from the compartment.

RONALD VINGOE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 683,492 Pictet Oct. 1, 1901 1,224,180 Lake May 1, 191'? 1,466,652 Batter Aug. 28, 1923 1,827,530 Le Grand Oct. 13, 1931 1,887,349 Hammond Nov. 8, 1932 1,945,407 Adair et al Jan. 30, 1934 2,165,996 Flosdorf June 27, 1939 2,359,796 Russell Oct. 10, 1944 FOREIGN PATENTS Number Country Date 345,672 Great Britain Mar. 23, 1931 OTHER REFERENCES Bergdoll, Stratochambers, Refrigeration Engi neering, Jan. 1943, pages 25-33. 

